(Applicant's Abstract) The Laboratory Core (Core B) will serve as a centralized facility for procedures that are common to two or more projects in the Core. An important task for the Core Laboratory is the processing of peripheral blood, obtained from the Clinical Core from its pool of well characterized donors. Centralization of this task will facilitate delivery of blood cells from the same donor to a Project (human monocytes and naive T cells), a Project (human basophils) and a Project (eosinophils, basophils and neutrophils). The Laboratory Core will also process human lung biopsies for functional microscopic analysis in 3 Projects. Core B technical staff will perform ELISAs for measurements of cytokines and histamine, as described in 4 Project. In addition, reconstruction studies described in 3 Projects will utilize murine mast cells, differentiated in Laboratory Core from precursors in mouse bone marrow.